How Irvin Osterloh raises continuous soybeans on marginal Wisconsin land

This 2020 season marks the 13th year Irvin Osterloh has raised continuous soybeans on his sandy loam farm in central Wisconsin. His bean yields in normal years have ranged from 45 to 55 bu. per acre. A few years ago with good weather, he won second place a regional soybean yield contest by harvesting 69 bu. per acre. He farms in Adams County, which has a 35-bu. county average yield.

May 5, 2020By Jerry Carlson — I met Irv in the 1980s. He hosted a field day on his farm during an outing from a Renewable Farming seminar I led at the Wisconsin Dells. More than 30 years ago, Irvin was enthused about soil biology — long before soil health became the catchword it is today. He's also a longtime WakeUP client.

What makes continuous beans give you reliable, gradually rising yields over the years? Companion crops. No-till.Foliar feeding, using WakeUP as a surfactant and mobilizer. Irv adapts long-established "biological ionization" principles taught by Dr. Carey Reams, one of history's most prescient ag consultants. Dr. Reams taught that with excellent soil biology, one or two species of perennial crops can thrive for generations — without rotation.

Irv has refined his nurse-crop management through the last three years of experimentation. Because of the farm's chilly latitude, fall-seeded cover crops like cereal rye are inconsistent. Each spring, Irv drills a fast-emerging oats crop as early as possible. He now uses the best-quality weed-free seed he can find. Typically that means buying carefully cleaned seed from Albert Lea Seed in Albert Lea, Minnesota. This company's current price for seed oats intended for cover cropping is $8.80 per bushel. Recommended seeding rate: 1.5 to 2 bushels per acre. (I've brought non-GMO seed and other agronomy supplies from Albert Lea Seed for many years.)

Usually, oats have four to six inches of growth by the time conditions are optimum for planting beans in May. This year, light rains are allowing Irv to start planting beans in some fields a little early.

The bottom five pictures below show how he used to plant 30-inch row soybeans into oats drilled on 7.5-inch centers. The first two photos below show his current tactic when drilling oats: plugging one metering gear every 30 inches. That creates a 15-inch wide alley with no oats. The 30-inch-row planter stitches beans into the center of each alley. That leaves two drilled rows of oats growing between soybean rows. The first photo is an example of that; the photo was taken after oats were terminated.

The growing oats provide an early shade on the soil. Apparently the white mold fungus, Sclerotinia sclerotiorum, senses this shading from oats, which triggers a premature explosion of mold spores — before the soybeans have developed enough to become infected. Irv noticed this phenomenon several years ago. "Avoiding white mold is important, because it's a mean animal," he says. When neighbors ask why he drills soybeans into oats, he points to a scientific paper on white mold which hangs in his shop, and explains how a spring cover of oats can help avoid serious white mold infection.

Also, I'd theorize that the rich array of mycorrhizal fungi colonizing the fine roots of oats may offer a competitive role against white mold. Microbiologist Dr. Robert Kremer, former USDA-ARS researcher at the University of Missouri, found that each species of cover crop encourages proliferation of about 10 species of beneficial fungi and bacteria. That's evident in breakdown of the oat stems and leaves each fall.

When oats reach about 10 inches high, Irv terminates them with herbicide, usually around June 10. "The residue from oats decomposes quckly, providing late-season nutrients to the soybeans," Irv points out. "By harvest time, you can't tell that oats were ever there."

I can envision that organic or non-GMO growers could adapt this nurse-crop system and avoid using a burndown herbicide. Irv says, "It would be easy to cultivate the oats from row middles." In fact, a devoted NO-tiller could adapt an implement with 20-inch electric rotary mower blades to shred the three strips of oats between soybean rows. Beans would quickly canopy over the mowed oats, stunting oats from regrowth.

In the counties around Irv's farm, there are several farmers who are clearing land and planting crops which can qualify as organic, because the land has never seen synthetic pesticides or fertilizers. Irv's technique could be helpful to them.

These photos provide a sequence of Irvin Osterloh's continuous-soybean system. Top three photos are from 2019. Remaining photos are from an earlier year, before he began leaving a 15-inch unsown strip for each soybean row.

Nurse-crop oats have been terminated, beans are thriving. The oats shade the ground and trick white mold organisms to "explode" spores prematurely, before beans are subject to infection. This is Irvin's 2019 crop.

Here's the 2019 soybeans that were planted into open strips between the oats nurse crop.

Another view of Irv's 2019 soybeans. He foliar-feeds with nutrients tank-mixed with WakeUP as a surfactant, penetrant and transporter in the crop.

Planting beans in live oats in 2018. Irv has since modified this to allow a 15-inch oats-free path for each row of soybeans.

Oats have been terminated, but they've established a dominance that helps reduce germination of late weeds.The burndown usually is scheduled for early June, when oats are about 10 inches tall.

With oats competition gone, beans quickly shade the middles to help hold down late-emerging weeds.

Irv dug a show-and-tell pit to reveal that his farm has about eight inches of loamy topsoil overlaying almost pure sand. Keeping a cover on the fields helps preserve moisture, even though oats use some moisture in early spring.

Healthy, weed-free soybeans at season's end. Irv's system has generated yields up to 73 bu. per acre. But the main gain is consistent yields and low cost.